JP2004338657A - Steering gear for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering gear for a vehicle allowing backup to a motor driving circuit and regular supply of electric power to a control unit during abnormality such as voltage drop only by providing a voltage monitoring means for monitoring supply voltage in each power supply for backup regardless of the number of power supplies. <P>SOLUTION: A first voltage monitor 51 detects supply voltage to the motor drive circuit 18 from a power supply 41 for the steering gear connected to the motor driving circuit 18, and a second voltage monitor 52 detects supply voltage from the power supply 41 for the steering gear and a power supply 42 for the vehicle to the control unit 200. When a monitored voltage value of the first voltage monitor 51 is less than a predetermined value and a monitored voltage value of the second voltage monitor 52 exceeds the predetermined value, abnormality is determined to occur in the power supply 41 for the steering gear, and the control unit 200 issues a changeover control command to a changeover circuit 5. The changeover circuit 5, after a lapse of a predetermined time, changes the power supply of the motor driving circuit 18 from the power supply 41 for the steering gear to the power supply 42 for the vehicle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steering device for a vehicle such as an automobile.
[0002]
[Prior art]
2. Description of the Related Art Power steering devices are widely and widely used in vehicle steering devices, particularly in automobile steering devices (see Patent Documents 1 and 2). As another example of a vehicle steering system, a steer-by-wire system in which a handle shaft and a wheel turning shaft are not mechanically connected but are electrically connected via a steering control unit is known. (See Patent Document 3). The steering control unit of these vehicle steering devices determines a steering output such as an assist torque or a steering angle to be applied to a wheel steering shaft in accordance with a steering input such as a steering torque or a steering angle applied to a steering handle shaft. Then, a method of controlling the rotation of the turning shaft drive motor so that the turning output is given to the wheel turning shaft is adopted.
[0003]
By the way, in the vehicle steering apparatus as described above, conventionally, the supply of the motor drive power to the steered shaft drive motor and the supply of the electric power to the vehicle electrical components except the steered shaft drive motor are common. And a common standby power supply (backup power supply) is provided in preparation for a voltage drop of the common power supply.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-168597 [Patent Document 2]
JP 2001-341656 A [Patent Document 3]
JP 2001-88727 A
[Problems to be solved by the invention]
By the way, when the voltage of the main power supply (power supply for the steering device) drops and the power supply is switched from the main power supply to the standby power supply (backup power supply), the power supply to the control unit for controlling the rotation of the steering shaft drive motor is not performed. If it is interrupted even temporarily, the steering control may become unstable. Therefore, a voltage monitor (voltage monitoring means) for constantly monitoring the supply voltage to the control unit is provided. In addition, in order to switch the power supply of the motor drive circuit from the main power supply to the standby power supply (or from the standby power supply to the main power supply) due to a power supply abnormality, it is necessary to set the power supply for each power supply capable of supplying the motor drive power to the motor drive circuit. A voltage monitor for monitoring the voltage is required separately from the voltage monitor on the control unit side. Therefore, a total of three voltage monitors are required even when there is one backup power supply, and the voltage monitor must be increased by one each time the backup power supply increases by one. It becomes a problem. In addition, as the abnormality of the power supply, disconnection or the like can be considered in addition to the voltage drop described above.
[0006]
An object of the present invention is to provide only one voltage monitoring means for monitoring a supply voltage to a motor drive circuit and a control unit irrespective of the number of backup power supplies. It is an object of the present invention to provide a vehicular steering apparatus that enables a backup of motor driving power to a motor driving circuit and a constant supply of motor control power to a control unit when the power generation occurs.
[0007]
Means for Solving the Problems and Effects of the Invention
In order to solve the above problems, a vehicle steering device according to the present invention includes:
A turning output to be given to the wheel turning shaft is determined in accordance with a steering input given to a steering handle shaft, and the rotation of the turning shaft drive motor is controlled so as to obtain the turning output by the wheel turning. In a vehicle steering device having a steering control unit that moves a rudder axis,
The vehicle is provided with a plurality of power supplies, and the plurality of power supplies supply motor driving power to a motor drive circuit that rotationally drives the steering shaft drive motor, and controls the rotation of the steering shaft drive motor. A power supply for a steering device for supplying power for motor control to a control unit to be controlled, and at least a backup power supply for backing up power for motor driving by the power supply for the steering device,
In the motor drive circuit, the power supply for the steering device and the backup power supply are arranged in parallel via switching means so that power for motor drive can be alternatively supplied. First voltage monitoring means for monitoring voltage is provided between the switching means and the motor drive circuit,
On the other hand, the steering unit power supply and the backup power supply are connected in parallel so that the motor control power can always be supplied to the control unit, and a second voltage for monitoring a supply voltage to the control unit is provided. A monitoring means is provided between the parallel connection part and the control unit.
[0008]
According to the vehicle steering system, the steering shaft drive motor is supplied with the motor drive power by using the power supply for the steering system as a dedicated power supply at normal times. Therefore, the capacity of the power supply for the steering device can be selected according to the steering shaft drive motor, and the motor drive power can be supplied stably. In addition, since the control unit (motor control circuit) is always supplied with motor control power from the steering device power supply and the backup power supply, even when an abnormality such as a voltage drop occurs in the steering device power supply, the motor is controlled. Stable steering control is ensured without causing troubles such as stoppage of supply of control power. Moreover, regardless of the number of backup power supplies, only the first voltage monitoring means for monitoring the supply voltage to the motor drive circuit and the second voltage monitoring means for monitoring the supply voltage to the control unit are provided. When an abnormality occurs in the power supply for the steering device, both the backup of the motor drive power to the motor drive circuit and the constant supply of the motor control power to the control unit become possible. Therefore, only one voltage monitoring means is provided for each of the motor drive circuit and the control unit. As the number of backup power supplies increases, it is advantageous in terms of manufacturing cost and layout space.
[0009]
When such a vehicle steering system includes a determination unit that determines whether or not an abnormality has occurred in a power supply for a steering system or a backup power supply based on a result of voltage monitoring by the first and second voltage monitoring units. In addition, switching of the motor driving power to the motor driving circuit can be easily performed. Therefore, even in the steer-by-wire type vehicle steering system, it is possible to avoid a state in which steering cannot be performed.
[0010]
Since the first and second voltage monitoring means can be set to the same threshold value, the first and second voltage monitoring means can be set to the first and second voltage monitoring means according to the rated voltage (for example, DC12V) of the vehicle-mounted battery normally used for the power supply for the steering device, the backup power supply and the like. What is necessary is just to set the threshold value (for example, DC10V) of the second voltage monitoring means. However, different thresholds may be set for the first and second voltage monitoring means.
[0011]
At this time, in order to further improve the stability of the steering control, the switching means uses the supply voltage to the control unit monitored by the second voltage monitoring means as a drive source based on a control signal from the control unit, and It is desirable to switch the power supply of the circuit. The supply voltage to the control unit is constantly supplied as motor control power from the steering device power supply and the backup power supply, and is constantly monitored by the second voltage monitoring means. Therefore, by using the supply voltage to the control unit as a drive source and operating the switching means based on a control signal from the control unit, the power supply of the motor drive circuit can be stably switched. For example, even when the supply voltage to the motor drive circuit by the power supply for the steering device falls below the threshold value of the first voltage monitoring means, the supply voltage to the control unit is not interrupted, so that the power supply to the motor drive circuit is steered. The power supply for the device can be switched to the power supply for the backup.
[0012]
Therefore, as the supply voltage value from the connection power supply, the voltage monitor value detected by the first voltage monitoring means is lower than the threshold value, and the voltage monitor value detected by the second voltage monitoring means is higher than the threshold value. At this time, the determining means determines that an abnormality has occurred in the connected power supply. By employing such a determination method, it is possible to determine the occurrence of an abnormality in the connected power supply by the two voltage monitoring means even if the number of backup power supplies increases.
[0013]
When the determining means determines that an abnormality has occurred in the connected power supply, the switching means switches the power supply of the motor drive circuit from the connected power supply to the non-connected power supply by switching the contacts of the relay, thereby stabilizing the steered shaft drive motor. And the reliability of the steering control is guaranteed.
[0014]
On the other hand, as the supply voltage value from the connection power supply, the voltage monitor value detected by the first voltage monitoring unit is lower than the threshold value, and the voltage monitor value detected by the second voltage monitoring unit is also lower than the threshold value. At this time, the determining means determines that an abnormality has occurred in the connected power supply and the non-connected power supply. By adopting such a determination method, even if the number of backup power supplies increases, the voltage monitor value and the threshold are compared by the two voltage monitoring means while sequentially switching the backup power supplies as connection power supplies. It is possible to determine whether an abnormality has occurred in the connected power supply and the non-connected power supply.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Example)
FIG. 1 schematically shows an entire configuration of a steer-by-wire type steering device as an example of a vehicle steering device to which the present invention is applied (in the present embodiment, “vehicle” is an automobile. However, the application object of the present invention is not limited to this. This vehicle steering system 1 is configured in a steer-by-wire system in which a handle shaft 3 directly connected to a steering handle 2 and a wheel steering shaft 11 are mechanically separated. A steering shaft drive motor (hereinafter, also simply referred to as a motor) 6 and a reduction mechanism 12 are coaxially mounted on the wheel steering shaft 11. Thus, the rotation of the motor 6 is transmitted to the wheel turning shaft 11 via the speed reduction mechanism 12, and the wheel turning shaft 11 reciprocates in the axial direction, so that the turning angle of the wheels 13, 13 changes.
[0016]
The angle position φ of the handle shaft 3 is detected as a steering angle (steering input) by a handle shaft angle detector 14 including a known angle detector such as a rotary encoder. On the other hand, the rotational angle position θ of the motor 6 is detected as a steered angle (steered output) by a motor angular position detecting unit 15 also composed of a rotary encoder or the like. Then, the steering control unit 20 determines the target rotation angle position θ ′ of the motor 6 based on the detected angle position φ of the handle shaft 3, and the rotation angle position θ of the motor 6 becomes the target rotation angle position θ ′. The operation of the motor 6 is controlled so as to approach.
[0017]
FIG. 2 is a block diagram of the vehicle steering system 1. The vehicle (vehicle steering device 1) includes a power supply unit 40 having a plurality of power supplies. In this embodiment, the power supply unit 40 includes a steering device power supply 41 that supplies motor driving power to the motor 6 and a vehicle power supply (for example, lamps, meters, and the like) other than the motor 6 that supplies power to vehicle electrical components (for example, lamps and meters). And a power supply 42. In the steering control unit 20, the power supply 41 for the steering device and the power supply 42 for the vehicle as a backup power supply can supply the motor drive power to the motor drive circuit 18 that drives the motor 6 alternatively. They are arranged in parallel.
[0018]
Specifically, the power supply 41 for the steering device and the power supply 42 for the vehicle are connected via the switching circuit 5 (switching means) of the steering control unit 20, the first voltage monitor 51 (first voltage monitoring means), and the power supply filter 22. The motor 6 is alternatively connected to a motor drive circuit 18 of the motor 6. That is, the first voltage monitor 51 is provided between the switching circuit 5 and the motor drive circuit 18. The switching circuit 5 disconnects the steering device power supply 41 from the motor drive circuit 18 when the voltage of the steering device power supply 41 (connected power supply) connected to the motor drive circuit 18 falls below a predetermined value (lower threshold). After confirming that the vehicle power supply 42 (unconnected power supply) does not have a ground fault and a voltage drop, the power supply of the motor drive circuit 18 is switched from the power supply 41 for the steering device to the power supply 42 for the vehicle.
[0019]
Similarly, the power supply 41 for the steering device and the power supply 42 for the vehicle are connected via a switching circuit 5 ′ (switching means) of the vehicle supply unit 30 and a drive circuit (such as a lamp or a meter) to a vehicle electrical component such as a lamp or a meter via the power supply filter 32. (Not shown). The switching circuit 5 ′ disconnects the vehicle power supply 42 from the drive circuit when the vehicle power supply 42 connected to the drive circuit drops below a predetermined value (lower threshold), and the steering device power supply 41 After confirming that there is no short circuit or voltage drop, the power source of the drive circuit is switched from the vehicle power source 42 to the steering device power source 41.
[0020]
In addition, the steering control unit 20 includes a control unit 200 (microcomputer) having a CPU 23, a RAM 24, a ROM 25, an input / output interface 26, and the like, and connecting these via a bus 27 so as to be able to transmit and receive. The power supply 41 for the steering device and the power supply 42 for the vehicle are connected at a point A (parallel connection part) via normally closed switches 29 and 29 and diodes 21 and 21 for backflow prevention, respectively. It is input to the voltage adjusting means 28 via the second voltage monitoring means). After that, the voltage controlled by the voltage adjusting unit 28 (for example, converted from DC + 12V to DC + 5V) is input to the input / output interface 26 of the control unit 200 or the like. The power supply 41 for the steering device and the power supply 42 for the vehicle are connected in parallel so that the control unit 200 that controls the rotation of the steering shaft drive motor 6 can always supply power for motor control.
[0021]
The input / output interface 26 includes an angle position φ of the handle shaft angle detection unit 14, a rotation angle position θ of the motor angle position detection unit 15, and respective voltages detected by the first voltage monitor 51 and the second voltage monitor 52. Monitor values and the like are input. On the other hand, from the input / output interface 26, a rotation control command for the motor 6 to the motor drive circuit 18, a switching control command (described later) to the switching circuit 5, and the like are output. The CPU 23 of the control unit 200 has a function as a determination unit that reads the power supply abnormality determination program stored in the ROM 25 and executes the program while using the RAM 24 as a work area to determine whether there is a power supply abnormality.
[0022]
The switching method of the power supply circuit connected to the motor drive circuit 18 by the switching circuit 5 will be described in detail with reference to FIGS. The first voltage monitor 51 detects (constantly monitors) the supply voltage to the motor drive circuit 18 from the power supply 41 for the steering device connected to the motor drive circuit 18, and the second voltage monitor 52 detects the power supply 41 for the steering device The supply voltage from the vehicle power supply 42 to the control unit 200 is detected (always monitored) (see FIG. 2). Then, the voltage monitor value of the first voltage monitor 51 is lower than a predetermined value (lower threshold; see FIG. 4B; for example, DC + 10 V), and the voltage monitor value of the second voltage monitor 52 is lower than a predetermined value (lower threshold; FIG. (See (b); for example, DC + 10V), it is determined that an abnormality (voltage drop, disconnection, etc.) has occurred in the power supply 41 for the steering device, and the control unit 200 (CPU 23) The following switching control command is issued. That is, the switching circuit 5 disconnects the power supply 41 for the steering device from the motor drive circuit 18, and after a predetermined time (delay time; see FIG. 4B; for example, one second) elapses, the power supply of the motor drive circuit 18 is steered. The power source 41 for the device is switched to the power source 42 for the vehicle.
[0023]
Specifically, as shown in FIG. 3, the switching circuit 5 includes a series circuit of a first electromagnetic relay 5b (R1; a relay) and a first electromagnetic relay driver 5x, and a second electromagnetic relay 5c (R2; a relay). And a series circuit with two electromagnetic relay drivers 5y. The first electromagnetic relay 5b (R1) and the second electromagnetic relay 5c (R2) are connected to the above-mentioned connection point A (parallel connection portion; see FIG. 2) at the potential (for example, DC + 12V) before adjusting the supply voltage to the control unit 200. More given. A normally closed contact 5d (R1-b) interlocked with the first electromagnetic relay 5b (R1) is provided in a circuit connected to the power supply 41 for the steering device. On the other hand, a normally open contact 5e (R2-a) interlocking with the second electromagnetic relay 5c (R2) is provided in a circuit connected to the vehicle power supply 42.
[0024]
As a result, the voltage monitor value of the first voltage monitor 51 for detecting the power supply 41 for the steering device connected to the motor drive circuit 18 (see FIG. 2) drops below a predetermined value, and the voltage of the second voltage monitor 52 decreases. When the monitored value exceeds a predetermined value, the normally closed contact 5d (R1-b) of the first electromagnetic relay 5b (R1) is switched to the open state, and the power supply 41 for the steering device is disconnected from the motor drive circuit 18. You. After a lapse of the predetermined time (a delay time set in advance and based on a clock signal from the CPU 23), the normally open contact 5e (R2-a) of the second electromagnetic relay 5c (R2) is switched to the closed state, and the motor drive circuit is turned off. The power supply 18 is switched from the power supply 41 for the steering device to the power supply 42 for the vehicle.
[0025]
As described above, the switching circuit 5 uses the supply voltage to the control unit 200 monitored by the second voltage monitor 52 as a driving source based on the control signal (switching control command) from the control unit 200 to supply the power to the motor driving circuit 18. Is switched. The supply voltage to the control unit 200 is always supplied as motor control power from the steering device power supply 41 and the vehicle power supply 42 and is constantly monitored by the second voltage monitor 52. The switching is performed stably, and the stability of the steering control is improved. That is, even when the supply voltage to the motor drive circuit 18 by the power supply 41 for the steering device falls below the lower threshold of the first voltage monitor 51, the supply voltage to the control unit 200 becomes lower than the lower threshold of the second voltage monitor 52. As long as the power supply does not fall below, the power supply of the motor drive circuit 18 can be switched from the power supply 41 for the steering device to the power supply 42 for the vehicle.
[0026]
Meanwhile, as shown in FIG. 4C, the voltage monitor value of the first voltage monitor 51 is lower than a predetermined value (lower threshold), and the voltage monitor value of the second voltage monitor 52 is also lower than the predetermined value (lower threshold). In this case, it is determined that an abnormality (voltage drop, disconnection, etc.) has occurred in the steering device power supply 41 and the vehicle power supply 42, and the control unit 200 (CPU 23) outputs an alarm output (warning display, warning sound, etc.). Do.
[0027]
In the switching means 5 'of the vehicle supply unit 30 shown in FIG. 2, the connection position between the normally closed contact 5d (R1-b) and the normally open contact 5e (R2-a) in FIG. used.
[0028]
Next, the contents of the power supply abnormality determination program executed mainly by the CPU 23 will be described with reference to the flowchart of FIG. First, the voltage value of the steering device power supply 41 (connection power supply) supplied to the motor drive circuit 18 (see FIG. 2) is monitored by the first voltage monitor 51 (see FIG. 2) (S1). It is checked whether is not less than the set lower threshold (S2). If the voltage monitor value is lower than the lower threshold (YES in S2), the supply voltage value to the control unit 200 is further monitored by the second voltage monitor 52 (see FIG. 2) (S3). It is checked whether the monitor value is below the set lower threshold (S4).
[0029]
At this time, if the voltage monitor value of the second voltage monitor 52 exceeds the lower limit threshold (NO in S4), it is determined that an abnormality such as a voltage drop or disconnection has occurred in the power supply 41 for the steering device, and the first The first electromagnetic relay 5b (R1) is operated via the relay driver 5x (S5). When the first electromagnetic relay 5b (R1) is excited, the normally closed contact 5d (R1-b) is opened, and the power supply 41 for the steering device is disconnected from the motor drive circuit 18 (S5; see FIGS. 4A and 4B). ). After the delay time has elapsed, the second electromagnetic relay 5c (R2) is operated via the second relay driver 5y (S6). By the excitation of the second electromagnetic relay 5c (R2), the normally open contact 5e (R2-a) is closed, and the vehicle power supply 42 is connected to the motor drive circuit 18 (S6; FIGS. 4A and 4B). reference).
[0030]
Next, the voltage value of the vehicle power supply 42 newly connected to the motor drive circuit 18 (see FIG. 2) is monitored by the first voltage monitor 51 (see FIG. 2) (S7), and the voltage monitor value is set. It is checked whether the value is below the lower limit threshold (S8). When the voltage monitor value falls below the lower limit threshold value (YES in S8), an abnormality such as a voltage drop or a disconnection occurs in the vehicle power supply 42 as the backup power supply following the steering power supply 41 that was the initially connected power supply. Is determined to have occurred, and a warning output (warning display, warning sound, etc.) is performed (S9).
[0031]
If the voltage monitor value of the second voltage monitor 52 is lower than the set lower threshold value in S4 (YES in S4), the voltage drop, disconnection, etc. occur in both the steering device power supply 41 and the vehicle power supply 42. Is determined to have occurred, and a warning output (warning display, warning voice, etc.) is performed as in S9 (S10).
[0032]
By providing the first voltage monitor 51 for monitoring the supply voltage to the motor drive circuit 18 and the second voltage monitor 52 for monitoring the supply voltage to the control unit 200, the following (1) and (2) All of ▼ became possible.
(1) Backup of motor driving power to the motor driving circuit 18 when an abnormality such as a voltage drop or disconnection occurs in the power supply 41 for the steering device;
(2) Constant supply of electric power for motor control to the control unit 200;
In addition, since only one voltage monitor is provided for each of the motor drive circuit 18 and the control unit 200, even if a backup power supply is added in addition to the vehicle power supply 42, no manufacturing cost or layout space is required.
[0033]
In addition, since there is a determination means for determining whether or not an abnormality has occurred in the power supply 41 for the steering device or the power supply 42 for the vehicle (backup power supply) based on the voltage monitoring results by the first voltage monitor 51 and the second voltage monitor 52. In addition, the switching of the motor drive power to the motor drive circuit 18 can be performed reliably and easily. Therefore, even in the steer-by-wire type vehicle steering system as in the present embodiment, it is possible to avoid a state in which steering is impossible.
[0034]
The above description has been made only for the steer-by-wire type steering device, but can also be applied to a power steering device. Also, an example in which a vehicle power supply is used as the backup power supply has been described, but the backup power supply may be a pure (dedicated) backup power supply that is not connected to the vehicle power supply. These vehicle steering devices include various types such as an electric type, an electro-hydraulic type, a variable steering output type such as a speed-sensitive type and a rotational speed-sensitive type. The power supply unit 40 may have a plurality of power supplies, and the number of steering control units and motors may be one or more. Further, these numbers can be appropriately combined. For example, a combination of two steering control units, one motor, one steering control unit, two motors, and the like can be selected.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a steer-by-wire type steering device as an example of a vehicle steering device to which the present invention is applied.
FIG. 2 is a block diagram of the vehicle steering system shown in FIG. 1;
FIG. 3 is a circuit configuration diagram of a switching circuit.
FIG. 4A is a timing chart of a switching circuit, and FIGS. 4B and 4C are graphs showing a change in a voltage monitor value by first and second voltage monitors.
FIG. 5 is a flowchart showing the contents of a power supply abnormality determination program.
[Explanation of symbols]
1 Vehicle steering system (steer-by-wire steering system)
3 Handle shaft 5 Switching circuit (switching means)
6. Motor (steering shaft drive motor)
11 Wheel turning shaft 18 Motor drive circuit 20 Steering control unit 23 CPU (determination means)
200 Control unit 40 Power supply unit 41 Power supply for steering device (connection power supply)
42 Vehicle power supply (backup power supply; unconnected power supply)
51 first voltage monitor (first voltage monitoring means)
52 Second voltage monitor (second voltage monitoring means)
A connection point (parallel connection part)

Claims (7)

A turning output to be given to the wheel turning shaft is determined in accordance with a steering input given to a steering handle shaft, and the rotation of the turning shaft drive motor is controlled so as to obtain the turning output by the wheel turning. In a vehicle steering device having a steering control unit that moves a rudder axis,
The vehicle is provided with a plurality of power supplies, and the plurality of power supplies supply motor driving power to a motor drive circuit that rotationally drives the steering shaft drive motor, and controls the rotation of the steering shaft drive motor. A power supply for a steering device for supplying power for motor control to a control unit to be controlled, and at least a backup power supply for backing up power for motor driving by the power supply for the steering device,
In the motor drive circuit, the power supply for the steering device and the backup power supply are arranged in parallel via switching means so that power for motor drive can be alternatively supplied. First voltage monitoring means for monitoring voltage is provided between the switching means and the motor drive circuit,
On the other hand, the steering unit power supply and the backup power supply are connected in parallel so that the motor control power can always be supplied to the control unit, and a second voltage for monitoring a supply voltage to the control unit is provided. A vehicle steering system, wherein monitoring means is provided between the parallel connection part and the control unit. 2. The vehicle steering system according to claim 1, further comprising a determination unit configured to determine whether an abnormality has occurred in the steering device power supply or the backup power supply based on a voltage monitoring result by the first and second voltage monitoring units. 3. apparatus. As the supply voltage value from a power source connected to the motor drive circuit (hereinafter, this power source is referred to as a connected power source and another power source is referred to as a non-connected power source) among the steering device power source and the backup power source, When the voltage monitor value detected by the one voltage monitoring unit is lower than the threshold value and the voltage monitor value detected by the second voltage monitoring unit is higher than the threshold value, the determination unit detects an abnormality in the connection power supply. The vehicle steering system according to claim 2, wherein it is determined that the occurrence of the steering wheel. When it is determined that an abnormality has occurred in the connection power supply by the determination unit,
4. The vehicle steering apparatus according to claim 3, wherein the switching unit switches a power supply of the motor drive circuit from the connection power supply to the non-connection power supply by switching a relay contact. 5. As a supply voltage value from the connection power supply, a voltage monitor value detected by the first voltage monitoring means is lower than a threshold, and a voltage monitor value detected by the second voltage monitoring means is also lower than the threshold. 5. The vehicle steering device according to claim 3, wherein the determination unit determines that an abnormality has occurred in the connected power supply and the non-connected power supply. The vehicle steering apparatus according to any one of claims 1 to 5, wherein the first and second voltage monitoring units are set to thresholds equal to each other. 2. The switching means for switching a power supply of the motor drive circuit based on a control signal from the control unit, using a supply voltage to the control unit monitored by the second voltage monitoring means as a drive source. The vehicle steering system according to any one of claims 1 to 6.

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